1. Field of the Invention
This invention relates generally to the treatment of a group of physiological disorders known as hyperhidrosis, or excessive sweating of the extremities or other parts of the body, by the electrical stimulation of the corresponding cluster of nerves and/or ganglia in the sympathetic chain and more specifically, for example, stimulation of the third or fourth thoracic ganglia is employed to treat palmar or axillary hyperhidrosis.
2. Description of the Prior Art
Within the field of neurosurgery, the use of electrical stimulation for the treatment of pathologies, including such disorders as uncontrolled movement, such as Parkinson""s disease and essential tremor, as well as chronic pain and eating disorders, has been widely discussed in the literature. It has been recognized that electrical stimulation holds significant advantages over alternative methods of treatment, for example lesioning, inasmuch as successful lesioning destroys all nerve activity. Collateral damage to non-targeted tissues is also a significant risk in lesioning treatments. In many instances, it is, therefore, the preferred effect is to stimulate or reversibly block nervous tissue. Electrical stimulation permits such stimulation of the target neural structures, and equally importantly, it does not require the destruction of the nervous tissue (it is a reversible process, which can literally be shut off or removed at will). In addition, stimulation parameters can be adjusted so that benefits are maximized, and side effects are minimized.
The particular application which the present invention is directed to, is the treatment of hyperhidrosis. For the purposes of providing details in the discussion to follow, palmar hyperhidrosis will be stressed. The principle symptom of this disorder is an excessive sweating of the palms. The disorder can be quite pronounced, and it effects hundreds of thousands of patients, many of whom are not simply embarrassed by the condition, but are in fact truly handicapped. These handicaps include constant wiping of hands, social avoidance, work avoidance, and difficulty performing tasks such as holding a steering wheel while driving. It has been estimated that 0.1-0.2% of young adults suffer from severe palmar hyperhidrosis. The cause of the condition is a dysfunction in the nerve cluster known as the cervicothoracic (lower stellate and upper thoracic) ganglia, which is one of the sequence of nerve clusters extending along the outside of the spinal column, and forms the sympathetic nervous system. The sympathetic, along with the parasympathetic, nervous system is part of the autonomic, or vegetative, nervous system. The effects of the autonomic system are extensive, and range from the control of blood pressure, heart rate, sweat, and body heat, to blood glucose levels, sexual arousal, and digestion. With respect to the current embodiment, the sympathetic outflow to the arm and hand originate in the lower portion of the stellate, and the first 3-4 thoracic ganglia. The sympathetic nervous system sends signals to cutaneous sweat glands via the release of acetylcholine (a common neurotransmitter) from postganglionic sympathetic nerve fibers. These peripheral nerve fibers synapse, or converge, in small nodes of nerve cells, called ganglia which lie alongside the vertebral bodies in the neck, chest, and abdomen. In particular, the stellate ganglion is located laterally adjacent to the intervertebral space between the seventh cervical and first thoracic vertebrae. The first, second, third and fourth thoracic ganglia lie next to their respective vertebral bodies on either side of the thoracic cavity. In patients suffering from palmar or other forms of hyperhidrosis, it is these ganglia which play a major role in the abnormal signal generation to the sweat glands of the hand. There is presently no effective medicinal treatment for the condition. The present standard of care for the interventional treatment of palmar hyperhidrosis is the lesioning of the stellate and upper thoracic ganglia via one of several surgical approaches.
While there are a variety of different techniques and mechanisms which have been designed to focus the lesioning means directly onto the target nerve tissue, collateral damage is inevitable. Were it even possible to direct all lesioning energy onto the target nerve cluster, it is a significant drawback that other functioning of these nerves is lost, even when such functioning may not be pathological. In addition, there are several common side effects described in the medical literature, including an ipsilateral Horner""s syndrome (drooping eyelid and smaller pupil), compensatory sweating (increased sweating in other areas), and gustatory sweating (sweating, particularly of the face, at the smell of certain foods). It is because of the development of these side effects that the initial satisfaction of current lesioning procedures has been reported to drop from over 98% to 66% over time.
These complications can be minimized to a large extent, or possible eliminated, by the use of chronic electrical stimulation or continuous drug infusion. The reasons are many, and include the possibility of changing which contacts of a multipolar lead are stimulated to minimize stimulating the superior portion of the stellate ganglion which can lead to a Homer""s syndrome, to adjusting the parameters such as frequency or pulse width to affect changes in compensatory and gustatory sweating, should they arise.
It is therefore the principle object of the present invention to provide a less destructive and fully reversible and adjustable method of treating palmar and other hyperhidrosis disorders.
The preceding objects are provided in the present invention, which comprises new and novel methods of treating hyperhidrosis disorders by implantation of stimulation electrodes at specific locations along the sympathetic chain. More particularly the present invention comprises a method of therapeutically treating palmar or other hyperhidrosis disorders, such as plantar or axillary hyperhidrosis, by surgically implanting an electrode adjacent to a predetermined site along the sympathetic chain on the affected side of the body, or if clinically indicated, bilaterally. For palmar or axillary hyperhidrosis, this involves the surgical implantation of a stimulating electrode over the inferior portion of the stellate ganglion, and over T2-4. The most commonly employed surgical approach is aided by video-assisted thoracoscopy, which involves the placement of 2-4 small incisions or ports in the chest wall, through which instruments may traverse en route to the lateral aspect of the vertebral bodies where the sympathic chain lies extrapleurally. The distal end of the lead can be secured to surrounding tissues and be placed either directly over the sympathetic chain or over the internal aspect of the parietal pleura. The proximal end of the lead can be passed out of the thoracic cavity via one of the neighboring surgical ports, and tunneled subcutaneously to an electrical signal source which, in turn, is operated to stimulate the predetermined treatment site over the sympathetic ganglia, such that the clinical effects of the hyperhidrosis disorder are reduced with minimal side effects.
Alternatively, a catheter with either end- or side-apertures placed over the ganglia of interest is connected in a similar fashion to a infusion pump. In addition, this embodiment is extended to include a combination electrical contact and drug delivery system, as well as a system which has the capacity to sense or record electrical or chemical activity in the region of interest